Komentaryo sa Genesis 23:1: Rashi, Bekhor Shor, Chizkuni & Da'at Zekenim

ויהיו חיי שרה מאה שנה ועשרים שנה ושבע שנים AND THE LIFE OF SARAH WAS 127 YEARS (literally, 100 years, 20 years and 7 years) — The reason the word שנה is written at every term is to tell you that each term must be explained by itself as a complete number: at the age of one hundred she was as a woman of twenty as regards sin — for just as at the age of twenty one may regard her as having never sinned, since she had not then reached the age when she was subject to punishment, so, too, when she was one hundred years old she was sinless — and when she was twenty she was as beautiful as when she was seven (Genesis Rabbah 58:1).

And the life of Sarah It is not the [usual] way to record the deaths of women, even righteous ones, unless it is by means of a deed. For behold we find only Sarah, Rachel, and Devorah -- Rivka's wetnurse -- and Miriam on the withdrawal of the well. Sarah's death is mentioned since she makes known to us how the grave was acquired with riches (and this is one of the tests [of Avraham]). Devorah's death is mentioned to make known how the name of the place is called Alon-Bachut. Rachel's death is mentioned to teach why she is not buried in Ma'arat haMachpela. And why is it that their years are not numbered, except for Sarah? Since she is the most important of them all.

ויהיו חיי שרה, “The years of Sarah’s life amounted to etc.” People fond of dabbling in the allusions found through the numerical value of words or whole sentences, will note that the numerical value of the word ויהיו equals the “life of Sarah,” in other words, Sarah’s real life commenced with the birth of Yitzchok, at which time she was 90 years old, whereas she died on the day of the binding of Yitzchok 37 years later. This is the numerical value of the word: ויהיו. As long as a person has no child he or she is considered as dead. (Talmud Nedarim, 64)